Abstract

A theoretical description of transient vibrational spectra following the impulsive optical excitation of a molecular system is presented. The approach combines the nonsecular evaluation of the Redfield equations to describe the dissipative dynamics of the system with an efficient implementation of the doorway-window formalism to calculate optical pump/infrared probe (vis/IR) spectra. Both parts of the calculation scale with , thus facilitating the treatment of systems with a dimension up to . The formulation is applied to a simple model of photoinduced electron transfer, which takes into account two coupled electronic states and a single anharmonic vibrational mode. Despite its simplicity, the model is found to exhibit quite complex electronic and vibrational relaxation dynamics, which in turn give rise to rather complex time- and frequency-resolved vis/IR spectra. Interestingly, the calculated IR spectra of the electron-transfer system predict the appearance of novel vibronically induced sidebands, which may even dominate the spectrum at early times.

Received 07 December 2005Accepted 21 December 2005Published online 20 March 2006

Acknowledgments:

We thank Peter Hamm, Michael Thoss, and Josef Wachtveitl for inspiring and helpful discussions. This work has been supported by the Frankfurt Center for Scientific Computing and the Deutsche Forschungsgemeinschaft.